Non-viral (synthetic) nucleic acid delivery systems have the potential to provide for the practical application of nucleic acid-based therapeutics. We have designed and created a tunable, self-assembling, non-viral nucleic acid delivery system that is based on cyclodextrin-containing polymers (CDP) and this delivery system has been shown to have very low toxicity in animals and give gene expression in targeted tissues from an intravenous administration. We propose to evaluate the hypothesis that our properly designed and engineered, synthetic, non-viral delivery vehicle bearing galactose-based targeting moieties can effectively deliver nucleic acids to hepatocytes in mice if the particle diameters do not exceed 70 nm and the surface charges are in the range of +/-10 mV. Specific Aims: 1. Formulate siRNA-containing, CDP-based particles with galactose-based targeting ligands of ca. 70 nm diameter or less with surface charges within the range of +/-10mV that can be recognized and processed by the asialoglycoprotein receptor on hepatocytes and determine the optimal physicochemical properties for maximum downregulation time and efficiency of a hepatic gene following systemic administration to mice. 2. Formulate plasmid DNA (pDNA)-containing, CDP-based particles using the conclusions obtained in Specific Aim 1 to guide the assembly and administration protocols and determine the gene delivery efficiency and the time course of gene expression in hepatocytes of mice using both marker and therapeutic genes. Significance: The development of effective, synthetic delivery vehicles for targeting hepatocytes would provide a generalized methodology for treating numerous diseases. Long-term goals: The potential for providing new disease treatments using nucleic acid-based therapies, the so-called gene therapies, has been restricted by limitations in the safe and effective delivery of nucleic acids. The long-term objective of our proposal is to design and engineer a generalized, synthetic system for ultimately delivering nucleic acid-based therapeutics to hepatocytes in humans.